This invention relates to an apparatus for cutting a layup of limp sheet material, such as fabric for making clothing or upholstery, and deals more particularly with a cutting machine having a vacuum hold-down system for compressing the layup of limp sheet material and a re-sealing system which lays down an overlay sheet onto the layup of material after cuts are made in it during a cutting operation so as to seal the cuts to effect continuous and even holding of the layup on the support surface during the remainder of the cutting operation. The vacuum holddown is one of the conveyorized type effecting bite-by-bite advancement and holding of a layup whose length is often several times longer than that of the support surface. The cutting operation is conducted on each bite of the layup length such that as one operation is completed on one segment of the layup length, another cutting operation begins on a new segment after the one segment it is advanced off the support surface and the new segment is advanced onto it.
Systems for sealing cuts made in a layup of sheet material during a cutting operation using an overlay sheet are known in automated cutting machines. In U.S. Pat. No. 4,542,673 issued to David Pearl on Sep. 24, 1985 and assigned to Gerber Garment Technology, Inc., it is disclosed therein to provide an apparatus for sealing the cut sheet material by providing an air impermeable sheet wound on a retractable roll carried by the cutting carriage assembly. The free or unwound end of the air impermeable sheet is held to a clamping bar at the discharge end of the cutting table and the sheet material is caused to pay out from the roll as the carriage moves away from the clamping bar during its cutting operation. With this arrangement, the entire mass of the roll of air impermeable sheet material is carried by the carriage along with the cutter head above the support surface. As a result, the carriage must be made from more substantial material than it would otherwise have to be to support both loads, thus increasing its manufacturing cost. Another approach is disclosed in U.S. Pat. No. 4,452,113 entitled METHOD AND APPARATUS FOR SEALING CUT SHEET MATERIAL issued to David Pearl on Jun. 5, 1984, and being commonly assigned to Gerber Garment Technology, Inc. Here an air impermeable overlay, which seals the sheet material when cut, is wound onto a roller which in turn is supported on a separate sealing roller carriage. This separate sealing carriage runs along tracks formed on the table and is mechanically coupled to the cutter head carriage so as to be slaved to its movements as the carriage is advanced during a cutting operation. Providing a separate sealing carriage as therein disclosed likewise has been found to increase the cost of production for a cutter as well as complicating its use. In U.S. Pat. No. 4,434,691 issued to Claude W. LeBlond on Mar. 6, 1984 and entitled METHOD AND APPARATUS FOR SEALING CUT SHEET MATERIAL, it is disclosed to pull a roller over the layup of sheet material using the cutter carriage to effect covering of the cuts made in the layup during a cutting operation. For this, a roll of air impermeable overlay material is rotatably mounted to the cutter carriage and is rolled over the layup with carriage as it is advanced during the cutting operation. The free end of the overlay material is connected to a drive roll which drivingly controllably rotates to take up the overlay with the bite of sheet material being advanced off the table. It is thus necessary to periodically shift the overlay material accumulating on the drive roller back to the overlay roller. Thus, the system employs a drive motor and drive associated with the drive roll to take up the overlay with the advancement of each bite which undesirably adds to the cost of manufacturing for the machine.
Accordingly, it is an object of the present invention to provide a layup re-sealing system wherein the overlay material is wound on a resealer roll that is not carried by a carriage and in which the free end of the overlay need not be secured to a controllably driven drive roller for purposes of maintaining a supply of the overlay material on the resealer roller for use in successive cutting operations.
Yet a further object of the present invention is to provide a sealing system whereby the overlay sheet and the table on which a layup of sheet material is supported effect full sealing engagement along the take-off end of the table.
A further object of the present invention is to provide a system for automatically re-sealing cuts made in a layup of the aforementioned type wherein the overlay sheet material continually is maintained in equilibrium between two rollers after every bite advancement and need not be periodically shifted after it accumulates on one of two rollers.
Other objects and advantages of the present invention will become apparent from the following description and the appended claims.